Thirty years into the HIV/AIDS epidemic evidence based prevention strategies remain critical to implement an effective public health response to human immunodeficiency virus (HIV). Effective prevention modalities implemented to scale have shown progress in slowing the spread of the disease within communities, but the work is not complete. Nowhere is this more evident than in the District of Columbia, where 3.2% of the population is diagnosed and living with HIV. At the end of 2008, there were 16,513 District residents living with HIV/AIDS, of whom 72.0% were male and 75.6% were Black. Dubbed a "Modem Epidemic," Washington, DC (DC) has concentrated epidemics among injecting drug users (IDU) and men who have sex with men (MSM), alongside a generalized epidemic among all District residents (3.2%). There is also evidence of striking disparities: 7.6% of people ages 40 to 49, 7.1% of black males, and 2.8% of black women in DC are living with HIV/AIDS. Among heterosexual communities at high risk, the National HIV Behavioral Surveillance (NHBS) system collected data on a community-based sample and found 5.2% of all participants, and as many as 6.3% of women, were HIV-positive. This proposal represents a continuation of the Public Health-Academic Partnership (established: 2006) between the District of Columbia, HIV/AIDS, Hepatitis, STD, and TB Bureau (HAHSTA) and the George Washington University School of Public Health and Health Services, Department of Epidemiology and Biostatistics (GW). Through this Partnership, and in collaboration with the community at large, NHBS has been successfully completed for each cycle it has undertaken FMSM (N=543). IDU (N=553). HET (N=825)1. This has allowed the District to use NHBS data to drive changes in HIV prevention policies and programs, including directing resources to scale up a comprehensive, evidence based, HIV prevention portfolio, shifting service paradigms locally, and working collaboratively with individual insurers, the public health system, community partners, and academia to slow the HIV/AIDS epidemic in the Nation's capital. The purpose of the NHBS system is to examine the prevalence of risk behaviors antecedent to acquisition of HIV in a population-based representative sample of individuals at high risk in areas with elevated HIV/AIDS rates. NHBS provides an improved understanding of behavioral risk factors, utilization of local prevention services and methods to reach the population in need of testing and care. NHBS also offers an estimate of what is happening among people not accessing HIV prevention or care settings: it allows insight into the depth of the epidemic among largely hidden populations that often wish to remain hidden. In this way, NHBS is essential in DC, as the local public health infrastructure grapples with a profound epidemic among people that are not always easily reached. In the proposed NHBS study in DC, five serial cross-sectional studies will be conducted, each year focusing on a specific population at high risk: men who have sex with men (MSM-3/4), injecting drug users (IDU-3/4), and heterosexuals at risk for HIV infection (HET-3). We also propose conducting additional modules to collect Hepatitis B, C, and syphilis data during each cycle, a respondent driven sample (RDS) of transgender male-to-females (MTF) during MSM-3, and evaluation of new HIV testing technologies in MSM-3. Through the partnership, HAHSTA has had demonstrated success in implementing NHBS with complete and on-time accrual each year, using RDS among IDU and heterosexuals, and venue based sampling (VBS) among MSM in partnership with a strong local academic institution. In this proposal, we outline plans to undertake the next five cycles, and three additional new objectives, with the highest regard for human subjects and surveillance data protection, community involvement, and scientific rigor in implementation and data dissemination. In addition to meeting past survey accrual goals, the Partnership has had other accomplishments of public health importance that will continue: these include collaboration with and dissemination to the local community planning groups (CPG), a well-defined GW Research Community Advisory Board with over 70 listed members, collaboration with multiple HAHSTA and GW Acuity and staff, and a unique opportunity for the training and development of the next generation of public health professionals.